1. Field of the Invention
This invention relates generally to metal forming and, in particular, to producing an extrusion preform from flat stock. Gear teeth and a cam surface may be formed by a cold extrusion process or by flow forming.
2. Description of the Prior Art
Cold extrusion of precision components, such as a helical ring gear, other gear forms, or a race having an inclined ramp for a one-way clutch, requires the use of preforms or blanks produced to tight tolerances. The current accepted practice involves producing the initial working stock by drawing a steel billet at high temperature over a cylindrical mandrel into a rough cylindrical shape, a process called “drawn over mandrel” (DOM). The stock, so formed, is then cut transversely into longitudinal sections, which are finish machined to tight dimensional tolerances.
The process is costly, requires high energy input, and results waste of raw material because considerable machining is required to produce dimensionally acceptable preforms.
Precision machining of a race for a one-way clutch of the type used in an automatic transmission requires several operations including machining a preform from a tube, cutting lobes with a broach tool, finish machining and final deburring.
Broach bars are expensive, require sulfonated broaching oils, need frequent sharpening and are slow relative to other machining or forming methods. Removal of oil from chips is costly and results in housekeeping concerns such as storing, transporting and disposal of chips and safety issues involved with oily surfaces. The oil is very expensive and must be filtered to remove fine metal particles before its reuse.
A need exists in the metal forming industry for a method to produce formed blanks and components. The blanks should be formed close to or fully net shape, thereby producing very little waste using conventional forming equipment normally available to manufacturing companies capable of extruding helical gears or similar products.
Preferably, the method would eliminate the need for custom processing at a steel supplier, and the preforms or blanks would be produced from flat plate or roll stock at a gear extrusion supplier.